The present invention relates to a writing instrument provided with an ink supply mechanism with a simple structure, and more particularly, to a writing instrument enabling an ink storing amount to be increased, and further enabling ink to be supplied stably to a writing element.
Conventionally, various writing instruments have been developed of so-called direct-ink type for directly storing liquid ink in an ink chamber. Such a type of writing instrument has an advantage of capable of storing a large amount of ink, but has disadvantages of requiring mechanisms with complicated structures for adjusting an ink pressure and controlling ink supply, etc. to stably supply the ink from an ink chamber to a writing element such as a ball chip and felt chip.
As described above, in order to stably supply the ink, it should be considered to compensate for expansion and contraction of the air in an ink chamber due to changes in temperature and barometric pressure and to compensate a hydraulic pressure of the ink from the ink chamber to the writing element in writing.
In order to overcome the above problems, there is known a writing instrument with a slide plug provided in an ink chamber as disclosed in Japan Laid-Open Patent Publication HEI7-20753. The slide plug is formed to be slidable in the axis direction with the ink densely filled in the ink chamber, partitions the ink chamber into a portion of the ink and a portion of the air, slides corresponding to consumption, expansion and contraction of the ink, and thereby always maintains a pressure of the ink in the ink chamber at an atmospheric pressure.
Such a plug type of writing instrument is excellent in ink pressure compensation function, but has inconveniences such that precision control in production and assembly is strict to enable the slide plug to smoothly slide with no resistance and thereby the cost is increased.
Further, as another type, there is a gas-liquid exchange/feeder type of writing instrument as disclosed in JP Patent 2534821. This type of writing instrument is configured so that a small amount of air is led into the ink chamber in return for the ink consumption, and thereby the ink pressure inside the ink chamber is always maintained to be equal to the atmospheric pressure. In this type of writing instrument, since the air is led into the ink chamber, adjacent to the ink chamber is provided a hollow chamber or labyrinthine passage called a feeder (reverser chamber) that holds the ink that is pushed out when the air expands due to, for example, changes in temperature.
In such a type of writing instrument, when the capacity of the ink chamber is increased to increase the ink storing amount, it is required to increase the capacity of a feeder corresponding to the increased chamber capacity. However, the size of writing instrument is limited to some extent, and in such a limited space, there is a limitation in increasing the capacity of an ink chamber.
Further, the gas-liquid exchange/feeder type of writing instrument generally has a structure in which a feeder communicating with the atmosphere side communicates with an ink chamber using a passage with a thin diameter. In the passage with a thin diameter, the ink is usually held by capillary force and is sealed. Then, when a pressure difference occurs between the ink chamber and the outside, the air is led into the ink chamber through the passage with a thin diameter, or the ink is pushed out of the ink chamber, and the pushed-out ink is stored in the feeder.
Such a type of writing instrument does not require a variable portion inherently and has a simple structure, but makes it difficult to lead the air into an ink chamber corresponding to ink consumption (gas-liquid exchange) and to hold and control the ink pushed out of the ink chamber, and thus has disadvantages that it is difficult to assure stable operations.
In other words, it is difficult to always seal a passage with a thin diameter under a constant condition with the ink, and as a result, there are problems that characteristics are not-stabilized, and the ink dries in the thin diameter, which is clogged. Thus, it is not possible to always obtain adequate stability and reliability.
Accordingly, it is an object of the present invention to provide a gas-liquid exchange/feeder type of writing instrument enabling an increased capacity of an ink chamber.
Further, it is a second object of the present invention to provide a gas-liquid exchange/feeder type of writing instrument with reliability in control of gas-liquid exchange and of pushed-out ink, with a simplified reliable structure, and with ease in production.
A writing instrument according to the present invention has an ink chamber formed inside a main body of the writing instrument, a writing element provided on a front end portion of the main body of the writing instrument, a reservoir chamber which is formed between the ink chamber and the writing element and communicates with the atmosphere and with the writing element, a plurality of walls which partitions the reservoir chamber and the ink chamber and further partitions the ink chamber into a plurality of small chambers in the axis direction, and an ink supply member which penetrates the plurality of walls and supplies ink from the ink chamber to the writing element, where each wall is provided with a communication hole capable of holding the ink by capillary force.
The communication hole formed in each wall is usually sealed with an ink membrane held by capillary force, and the ink in the ink chamber is supplied to the writing element through the ink supply member. When letting the writing instrument stand for use in writing, since the communication hole at a lower side of the ink chamber is sealed with the ink membrane, the ink chamber is sealed in the vertical direction. As a result, the hydraulic pressure corresponding to length of the ink chamber is canceled, and therefore, does not affect the writing element.
Further, when the ink is consumed, or the ink and/or air in the ink chamber contracts due to changes in temperature, etc, the seal due to the ink membrane of the communication hole formed in the wall between the reservoir chamber and ink chamber is broken, and a small amount of air is led from the reservoir chamber into the ink chamber, thereby preventing an occurrence of a negative pressure inside the ink chamber. When the ink and/or air in the ink chamber expands due to changes in temperature or the like, the seal due to the ink membrane of the communication hole formed in the wall between the reservoir chamber and ink chamber is broken, and the ink is pushed out of the ink chamber to the reservoir chamber, thereby canceling the expansion in pressure inside the ink chamber. In addition, a configuration is preferable in which the ink pushed into the reservoir chamber is fed to the writing element to be consumed or returned to the ink chamber when the pressure inside the ink chamber becomes a negative pressure.
The ink chamber is partitioned into a plurality of small chambers in the axis direction by at least one wall. When the ink is consumed, the ink is consumed in a first small chamber nearest the reservoir chamber where the gas and liquid are exchanged, and the air is led to only the first small chamber from the reservoir chamber. Accordingly, even when the ink in the first small chamber is almost replaced with the air, since the capacity of the first small chamber is small, a small amount of air expands due to changes in temperature or the like, and therefore an amount of ink pushed into the reservoir is small.
Further, after the first small chamber becomes empty, the gas and liquid are exchanged between the first and second small chambers, and the air is led into the second small chamber. In this case, the ink pushed out of the second small chamber is held in the first small chamber. In other words, after the first small chamber becomes empty, the first small chamber serves as a reservoir chamber, and thereafter, another small chamber becoming empty servers as a reservoir chamber sequentially.
By such a consecutive operation, it is possible to decrease the capacity of the reservoir chamber communicating with the writing elements, and corresponding to the decreased capacity, it is possible to increase the capacity of the entire ink chamber and to store a larger amount of ink.
Further, this writing instrument has such a simple structure that the inside of the main body of the writing instrument is partitioned using a plurality of walls, thereby forming small chambers serving as a reservoir chamber and ink chamber, a communication hole of ink is formed in each wall, and that an ink supply member penetrates and is inserted through the walls, does not have any variable portion, thereby having simple operations, and therefore is high in reliability and easy in production.